Osteoarthritis (OA) is one of the most common disorders of humans. Osteoarthritis is a major cause of morbidity in the population over 50 and affects more than 40 million Americans. It also imposes considerable expense on the health care system. Although evidence implicates cartilage degeneration as the primary cause for OA, no cure exists as yet. Current treatments relieve symptoms but do not inhibit disease progression. Therefore, the development of new treatments is of utmost importance. Ideally, methods should target the early stages of the disease. However, the development of promising new therapies is hindered by the lack of noninvasive methods to detect early stages of cartilage degeneration. In order to address this, one needs to understand the structural and biochemical changes that occur during degeneration and to correlate these properties to measurable parameters obtained by a noninvasive method. The applicants proposed to exploit MR properties of sodium to monitor structural and biochemical changes in cartilage in order to determine the extent of the cartilage degeneration. They proposed to measure MR properties of sodium by imaging and by spectroscopy. The measurements will be made on normal bovine cartilage, on bovine cartilage (in which proteoglycans are removed selectively to mimic the structural and biochemical changes that occur in OA), and on human cartilage plugs with different stages of OA. The results obtained from the enzymatically degraded studies will be correlated to the osteoarthritic human specimens which have been histologically graded to assess the extent of degeneration. The measured MR properties rely not only on tissue sodium content and thereby contrast, but are also dependent on structural and biochemical changes. Therefore, this proposed research will aid in the early diagnosis of OA as well as aid in the development of drugs and treatment therapies.